Question

Mihai si David au impreuna 55 de cartonase,Mihai si Radu au impreuna 77 de cartonase , iar David si Radu au 90 de cartonase.Afla cate cartonase are fiecare copil?Va rog!

Answer 1

M+D=55
M+R=77
D+R=90
2M+2D+2R=55+77+90
2M+2D+2R=222

dam factor comun pe 2 si vom avea:
2(M+D+R)=222
M+D+R=222:2
M+D+R=111

111-55=56 cartonase Radu
111-77=34 cartonase David
111-90=21 cartonase Mihai

proba:
21+34=55 
21+56=77
34+56=90